The reason I got this is because my sister wont play unless I turned my gun down more than is possible with the stock adjustment. So far I haven't had any problems with it. You do need to tighten the lock-down screw or it will work its way out dropping your fps even more; or even worse it could fall out and lose your drive spring and pin out of your marker. when I am not shooting my sister I like to open up the "bolt fps adjustment" and screw the adjuster out. this should make the gun more air efficient (just a theory so far. ill let you know when I am sure). also Im sure some of you have had to cut your spring when you bought upgrades on some guns. With this upgrade you will be able to lessen the tension on the spring without cutting anything. If I learn anything with more use I will come back and edit this review more. I bought one for mine and my brother-in law's A-5.

Conclusion:

not a necessity in most cases. I just couldn't turn the gun down to 240 fps without it. Most people wont need to or want to. If it does help my air efficiency at 280 It will be totally worth it. I will hope for the best and give it a 10